The invention relates to a night vision device and in particular to a monocular night vision device.
Monocular night vision devices are essentially designed according to the following principle. A, preferably fast, lens focuses the rays emanating from an object to be observed onto an entry window of a low-light-level amplifier. The image of the object is electrically amplified there and, owing to the phosphorescent coating on the exit of the low-light-level amplifier, appears as a bright green image on its exit window. The substantial feature of the low-light-level amplifier in this context is that it is provided with an inverter (image inversion system) which inverts the amplified green image of the object. This green image is projected via an eyepiece into the user""s eye. Equipping the low-light-level amplifier with an inverter is expensive, and the length and the weight of the low-light-level amplifier increase substantially.
On the other hand, instead of by means of an inverter, it is possible to invert the electronically amplified green image of the object by means of a separate optical inverter which then projects the image through an eyepiece into the eye. However, the result is virtually the same because, in the case of conventional inverters formed from lenses, the result is then a long, heavy and relatively expensive (monocular) night vision device.
In contrast, it is the object of the invention to provide a night vision device, in particular a monocular night vision device, which requires neither a low-light-level amplifier with a conventional inverter nor a separate optical system for the image inversion. As a result of these circumstances, it should be possible substantially to reduce length, weight and manufacturing costs of the device.
This can be achieved, according to the invention, by realizing the characterizing features of Claim 1 and those of Claim 10. When it is stated that the optical axis passing through the lens of the device should be xe2x80x9cessentiallyxe2x80x9d parallel to the axis leading to the receptor, small deviations from parallelism may result from a parallax compensation. When it is stated that the beam path between the exit window of the low-light-level amplifier and the receptor is determined by reflective optical elements, this by no means rules out that lenses too, i.e. refractive elements, are concomitantly used, for example for changing the magnification factor.
Advantageous alternative embodiments are described by the features of the dependent Claims.
In the invention, in principle the refractive optical parts between the low-light-level amplifier and the human eye are replaced by reflective ones, which reduces the manufacturing costs for the device according to the invention. With respect to the comfort of wear, too, this represents a not inconsiderable reduction in weight and assembled length. In addition, the achievement according to the invention, comprising reflective optical elements, still has the property of being able to observe the object directly (for example as through sunglasses) and at the same time of seeing its amplified, in general green imagexe2x80x94superposed on the xe2x80x9cdirectxe2x80x9d image.